Simultaneous Chaos Time-Delay Signature Cancellation and Bandwidth Enhancement in Cascade-Coupled Semiconductor Ring Lasers

Optics chaos has been widely studied and its various applications have also been demonstrated in recent years. To improve the performance of chaos-based applications, several properties of the chaotic signals should be evaluated and enhanced accordingly. In this paper, we consider a chaotic system consisting of three cascade-coupled semiconductor ring lasers (SRLs), where the master SRL is subjected to conventional (parallel) optical feedback, while its output is injected to the intermediate SRL and further to the slave SRL. We focus on the time-delay signature (TDS) and bandwidth of the generated chaos and demonstrate the possibility of the simultaneous realization of TDS elimination and bandwidth enhancement in the parameter space of the injection strength against the frequency detuning. In addition, a proof-of-concept test of randomness is carried out, and it demonstrates that the chaotic properties could be greatly enhanced by the proposed cascade-coupling scheme compared with a single SRL with feedback and thus is suitable for use in high-speed random number generation.